正火温度对钢轨窄间隙自动电弧焊焊接接头硬度和组织的影响

摘要

PD3 rails were welded by narrow-gap automatic arc welding, then simulated normalization was performed for the joints in the temperature range of 800-975 ℃. The effects of the normalization temperature on the hardness and microstructure of the joints were investigated by microstructure observation and microhardness testing. The results show that the welding seam microstructure without normalizing was lower bainite with coarse grains. And the grains near the bond area were coarser with lots of retained austenite. With the increase of the normalization temperature, the welding grains were refined, the martenite proportion increased gradually.Meanwhile the microstructure of the welding at 925 ℃ was refined bainite and martenite. And the hardness of the softening region of the joint annealed at the temperature was equivalent to that of the base material.%采用自动电弧焊焊接得到了PD3钢轨的窄间隙焊接接头,对其进行了温度为800～975℃的模拟正火处理,通过显微组织观察和显微硬度测试,研究了正火温度对接头硬度和组织的影响.结果表明:焊后未经热处理的接头焊缝组织为晶粒粗大的下贝氏体,熔合区附近晶粒更加粗大,并有一定量的残余奥氏体;随着正火温度的升高,焊缝组织得到细化,马氏体的含量逐渐增加,其中925℃时焊缝组织为细小的贝氏体、马氏体,并且在此温度正火后接头软化区的硬度与母材的相当.